Up-drawing continuous casting apparatus and up-drawing continuous casting method

ABSTRACT

An up-drawing continuous casting apparatus includes a holding furnace which holds molten metal, a guide-out member which guides the molten metal out from a surface of the molten metal held in the holding furnace, a shape determining member which is arranged to adjoin the surface of the molten metal and allows the molten metal guided out by the guide-out member to pass through the shape determining member to define a shape of a cross section of a casting, a cooling portion which cools the molten metal after the molten metal passes through the shape determining member, and an impact imparting portion which imparts an impact to the guide-out member or the casting.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an up-drawing continuous casting apparatus and an up-drawing continuous casting method.

2. Description of Related Art

In Japanese Patent Application Publication No. 2012-61518 (JP 2012-61518 A), the inventors have been suggesting a free casting method as an epoch-making continuous casting method which requires no mold. As disclosed in JP 2012-61518 A, after a starter is immersed in a surface of molten metal, the starter is pulled up, and molten metal is then guided out following the starter via a surface film and surface tension of the molten metal. Here, the molten metal is guided out via a shape determining member arranged to adjoin the surface of molten metal and cooled, thereby enabling continuous casting for producing castings having desired cross-sectional shapes.

In a conventional continuous casting method, a mold defines a cross-sectional shape and a longitudinal shape. Particularly, in a continuous casting method, because solidified metal (that is, a casting) has to pass through the inside of a mold, a produced casting has a shape linearly extended in a longitudinal direction. In contrast, the shape determining member in the free casting method only defines the cross-sectional shape of the casting but does not define the longitudinal shape. Furthermore, the shape determining member is moveable in a direction parallel to the surface of molten metal (that is, a left-right direction), thus allowing obtainment of castings having various longitudinal shapes. For example, JP 2012-61518 A discloses a hollow casting (that is, a pipe) which is not longitudinally linear and formed into a zigzag shape or a helical shape.

The inventors found the following problems. The free casting method disclosed in JP 2012-61518 A can form a casting having a continuous shape by the shape determining member. However, it is difficult to form a casting in a discontinuous shape. Further, even if the shape determining member is momentarily moved, it is difficult to provide a discontinuous shape to a held molten metal before solidification.

SUMMARY OF THE INVENTION

The present invention provides an up-drawing continuous casting apparatus and an up-drawing continuous casting method which can form a discontinuous shape on a surface of a casting produced by continuous casting.

A first aspect of the present invention relates to an up-drawing continuous casting apparatus. The up-drawing continuous casting apparatus includes: a holding furnace which holds molten metal; a guide-out member which guides the molten metal out from a surface of the molten metal held in the holding furnace; a shape determining member which is arranged to adjoin the surface of the molten metal and allows the molten metal guided out by the guide-out member to pass through the shape determining member to define a shape of a cross section of a casting; a cooling portion which cools the molten metal after the molten metal passes through the shape determining member; and an impact imparting portion which imparts an impact to the guide-out member or the casting.

Such an aspect enables formation of a discontinuous shape on the surface of the casting.

In the above aspect, the impact imparting portion may impart an impact to the guide-out member or the casting by striking the guide-out member or the casting with a metal rod.

In the above aspect, the impact imparting portion may move along a moving path of the guide-out member.

Accordingly, the impact imparting portion can impart an impact to the guide-out member or the casting anytime during progress of casting.

Meanwhile, in the above aspect, the impact imparting portion may be an oscillator.

This enables formation of a discontinuous shape on the surface of the casting, enhancement of surface tension of a held molten metal, and more precise formation of the casting in a desired shape.

In the above aspect, the impact imparting portion may be fixed to the guide-out member while contacting with the guide-out member.

Accordingly, the impact imparting portion can impart an impact to the guide-out member anytime during the progress of casting.

A second aspect of the present invention relates to an up-drawing continuous casting method. The up-drawing continuous casting method is carried out by use of a casting apparatus including: a guide-out member which guides molten metal out; a shape determining member which defines a shape of a cross section of a casting; and an impact imparting portion which imparts an impact to the guide-out member or the casting. The up-drawing continuous casting method includes: guiding the molten metal out by the guide-out member to allow the molten metal to pass through the shape determining member; cooling the molten metal after the molten metal passes through the shape determining member; and imparting an impact to the guide-out member or the casting by the impact imparting portion.

Such an aspect enables formation of a discontinuous shape on the surface of the casting.

In the above aspect, imparting an impact to the guide-out member or the casting may be carried out by striking the guide-out member or the casting with a metal rod by the impact imparting portion.

In the above aspect, the method may include moving the impact imparting portion along a moving-path of the guide-out member.

Accordingly, the impact imparting portion can impart an impact to the guide-out member or the casting anytime during progress of casting.

Meanwhile, in the above aspect, the impact imparting portion may be an oscillator.

This enables formation of a discontinuous shape on the surface of the casting, enhancement of surface tension of a held molten metal, and more precise formation of the casting in a desired shape.

In the above aspect, the impact imparting portion may be fixed to the guide-out member while contacting with the guide-out member.

Accordingly, the impact imparting portion can impart an impact to the guide-out member anytime during the progress of casting.

The first and second aspects of the present invention can provide an up-drawing continuous casting apparatus and an up-drawing continuous casting method which can form a discontinuous shape on a surface of a casting produced by continuous casting.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a cross-sectional view of a free casting apparatus in accordance with a first embodiment of the present invention;

FIG. 2 is a plan view of an inner shape determining member and an outer shape determining member in FIG. 1;

FIG. 3A is a schematic diagram for illustrating a formation process of a casting by the free casting apparatus in accordance with the first embodiment of the present invention;

FIG. 3B is a schematic diagram for illustrating the formation process of a casting by the free casting apparatus in accordance with the first embodiment of the present invention;

FIG. 3C is a schematic diagram for illustrating the formation process of a casting by the free casting apparatus in accordance with the first embodiment of the present invention;

FIG. 4 is a view for illustrating one example of a casting formed by the free casting apparatus in accordance with the first embodiment of the present invention; and

FIG. 5 is a cross-sectional view of a free casting apparatus in accordance with a second embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Specific embodiments to which the present invention is applied will be described in detail hereinafter with reference to drawings. However, it should be noted that the present invention is not limited by the following embodiments. Further, the following descriptions and drawings are appropriately simplified for the purpose of clarifying the descriptions. It should be noted that a “top-bottom direction,” a “left-right direction,” and the like used in the following descriptions correspond to the left-right and top-bottom directions in the drawings.

First Embodiment

A free casting apparatus (up-drawing continuous casting apparatus) in accordance with a first embodiment will first be described with reference to FIG. 1. FIG. 1 is a cross-sectional view of the free casting apparatus in accordance with the first embodiment. As shown in FIG. 1, the free casting apparatus in accordance with the first embodiment includes a molten metal holding furnace 101, an inner shape determining member 102 a, an outer shape determining member 102 b, support rods 103, 104, an actuator 105, a cooling gas nozzle 106, and an impact imparting portion 107.

The molten metal holding furnace 101 houses molten metal M1 such as aluminum or its alloy and keeps the molten metal at a prescribed temperature. In an example of FIG. 1, because the molten metal holding furnace 101 is not refilled with molten metal during the casting, a surface of the molten metal M1 moves down as the casting progresses. On the other hand, the molten metal holding furnace 101 may constantly be refilled with molten metal during the casting to sustain the surface of molten metal. It is a matter of course that the molten metal M1 may be metals and alloys other than aluminum.

The inner shape determining member 102 a and the outer shape determining member 102 b are formed from ceramics, stainless steel, or the like, for example, and are arranged to adjoin the surface of molten metal. In the example of FIG. 1, the inner shape determining member 102 a and the outer shape determining member 102 b are arranged to contact with the surface of molten metal. However, the inner shape determining member 102 a and the outer shape determining member 102 b may be arranged such that main surfaces on their lower sides (sides facing the surface of molten metal) do not contact with the surface of molten metal. Specifically, prescribed gaps (for example, approximately 0.5 mm) may be provided between the main surfaces of the inner shape determining member 102 a and the outer shape determining member 102 b on their lower sides and the surface of molten metal.

The inner shape determining member 102 a defines an inner shape of a casting M3. The outer shape determining member 102 b defines an outer shape of the casting M3. The casting M3 shown in FIG. 1 is a hollow casting in which the shape of a cross section in the left-right direction (hereinafter referred to as left-right cross section) is tubular (that is, a pipe). In other words, more specifically, the inner shape determining member 102 a defines an inner diameter of the left-right cross section of the casting M3, and the outer shape determining member 102 b defines an outer diameter of the left-right cross section of the casting M3.

FIG. 2 is a plan view of the inner shape determining member 102 a and the outer shape determining member 102 b. Here, the cross-sectional view of the inner shape determining member 102 a and the outer shape determining member 102 b in FIG. 1 corresponds to a cross-sectional view taken along line I-I in FIG. 2. As shown in FIG. 2, the outer shape determining member 102 b has a rectangular planar shape, for example, and has a circular opening in its central portion. The inner shape determining member 102 a has a circular planar shape and is arranged in a central portion of the opening of the outer shape determining member 102 b. A gap between the inner shape determining member 102 a and the outer shape determining member 102 b is a molten metal passing portion 102 c through which molten metal passes. As described above, a shape determining member 102 is configured with the inner shape determining member 102 a, the outer shape determining member 102 b, and the molten metal passing portion 102 c.

As shown in FIG. 1, the molten metal M1 is pulled up following a starter (guide-out member) ST or the casting M3 via a surface film and surface tension of the molten metal and passes through the molten metal passing portion 102 c. Here, the molten metal pulled up following the starter ST or the casting M3 via the surface film and the surface tension of the molten metal will be referred to as a held molten metal M2. Further, an interface between the casting M3 and the held molten metal M2 is a solidification interface.

The support rod 103 supports the inner shape determining member 102 a. The support rod 104 supports the outer shape determining member 102 b. The support rods 103, 104 enable sustainment of a positional relationship between the inner shape determining member 102 a and the outer shape determining member 102 b. Here, forming the support rod 103 into a pipe structure, feeding cooling gas through that, and providing a blowout hole in the inner shape determining member 102 a allow cooling of the casting M3 from its inside.

The actuator 105 is connected with both the support rods 103, 104. The support rods 103, 104 are moveable in the top-bottom direction and a left-right direction while sustaining the positional relationship between the inner shape determining member 102 a and the outer shape determining member 102 b. Such a configuration allows the inner shape determining member 102 a and the outer shape determining member 102 b to move down following the surface of molten metal which moves down as the casting progresses. Further, the inner shape determining member 102 a and the outer shape determining member 102 b can be moved in a left-right direction, and the longitudinal shape of the casting M3 can thereby be freely changed.

The cooling gas nozzle (cooling portion) 106 is for blowing cooling gas (such as air, nitrogen, or argon) to the starter ST and the casting M3 to cool those. A pulling-up device (not shown) coupled to the starter ST pulls up the casting M3, and the cooling gas cools the starter ST and the casting M3. Accordingly, the held molten metal M2 adjoining the solidification interface is sequentially solidified, thereby continuously forming the casting M3.

The impact imparting portion 107 is a member which imparts an impact to the starter ST or the casting M3. The impact imparting portion 107 imparts an impact to the starter ST or the casting M3 by striking the starter ST or the casting M3 with a metal rod, an air hammer, an electric hammer, or the like, for example. The impact imparted to the starter ST or the casting M3 by the impact imparting portion 107 is transmitted through the casting M3. As a result, a slight relative displacement is momentarily produced between the casting M3 and the held molten metal M2 across the solidification interface. The held molten metal M2 adjoining the solidification interface where the momentary relative displacement is produced solidifies to form the casting M3 which has a discontinuous shape on its surface. More specifically, the held molten metal M2 adjoining the solidification interface where the momentary relative displacement is produced solidifies to form the casting M3 which has a linear shape of a prescribed width (for example, a width of approximately 0.1 mm) on its surface. The discontinuous shape (linear shape) formed on the surface of the casting M3 (such that the shape is formed around the outer circumference of the surface) is used as a marking off line for specifying a reference position in the casting M3, for example.

The impact imparting portion 107 is moveable along a moving path of the starter ST. For example, the impact imparting portion 107 is moveable in an upward direction following an upward movement of the starter ST by a pulling-up operation of the pulling-up device (not shown). Accordingly, the impact imparting portion 107 can impart an impact to the starter ST or the casting M3 anytime during the progress of casting.

Further, the strength of the impact imparted to the starter ST or the casting M3 by the impact imparting portion 107 is sufficient as long as a visible marking off line can be formed on the surface of the casting M3 and should at least be limited to the degree that the shape of the casting M3 as a whole is not influenced. The most effective direction for imparting an impact is a perpendicular direction to the pulling-up direction (a left-right direction); however, the direction may be in parallel with the pulling-up direction or oblique to the pulling-up direction.

A free casting method in accordance with the first embodiment will next be described with reference to FIGS. 1, 3A, 3B, and 3C. FIGS. 3A, 3B, and 3C are schematic diagrams for illustrating a formation process of the casting M3 by the free casting apparatus shown in FIG. 1 over time.

The starter ST is first moved down, and a distal end portion of the starter ST is immersed in the molten metal M1 through the molten metal passing portion 102 c between the inner shape determining member 102 a and the outer shape determining member 102 b.

Pulling up of the starter ST is next started at a prescribed speed. Here, even though the starter ST separates from the surface of molten metal, the molten metal M1 is pulled up (guided out) from the surface of the molten metal following the starter ST and forms the held molten metal M2 (see FIG. 3A). As shown in FIG. 1, the held molten metal M2 is formed by the molten metal passing portion 102 c between the inner shape determining member 102 a and the outer shape determining member 102 b. In other words, the inner shape determining member 102 a and the outer shape determining member 102 b provide a shape to the held molten metal M2.

Next, because the starter ST (and the casting M3) is cooled with the cooling gas blown from the cooling gas nozzle 106, the held molten metal M2 is sequentially solidified from its upper side to its lower side, thereby growing the casting M3. Accordingly, the casting M3 can be produced by the continuous casting.

Here, while casting is in progress, the impact imparting portion 107 imparts an impact to the starter ST or the casting M3. As a result, a slight relative displacement is momentarily produced between the casting M3 and the held molten metal M2 across the solidification interface (see FIG. 3B).

Further, the held molten metal M2 adjoining the solidification interface where the momentary relative displacement is produced solidifies to form the casting M3 which has a discontinuous shape on its surface. For example, a marking off line K1 as the discontinuous shape is formed on the surface of the casting M3 (see FIG. 3C).

FIG. 4 is a view for illustrating one example of the casting M3 formed by the free casting apparatus shown in FIG. 1. In the example of FIG. 4, the marking off line K1 is formed on an upper side of the casting M3 which has a smoothly curved cylindrical shape, and a marking off line K2 is formed on its lower side. As described above, in a case of the casting M3 in a cylindrical shape or the like with no corner, the plurality of marking off lines K1, K2 are provided on the surface of the casting M3, thereby allowing specification of a reference position in three directions (x, y, z directions) in the casting M3.

As described above, the free casting apparatus in accordance with this embodiment includes the impact imparting portion 107 which imparts an impact to the starter ST or the casting M3. Accordingly, the free casting apparatus in accordance with this embodiment can form a discontinuous shape (linear shape) on the surface of the casting M3 produced by the continuous casting. The discontinuous shape formed on the surface of the casting M3 is used as a marking off line for identifying a reference position in the casting M3, for example. This allows reduction in working time compared to a case where a marking off line is provided to the casting M3 by a separate step after casting.

The free casting apparatus in accordance with this embodiment imparts an impact to the starter ST or the casting M3 instead of imparting an impact to the shape determining member 102. This allows prevention of dimensional errors in the casting M3 and contamination of the casting M3 with foreign objects (such as oxides) that may occur due to a momentary movement of the shape determining member 102. Further, the free casting apparatus in accordance with this embodiment imparts an impact to the starter ST or the casting M3 by the impact imparting portion 107 instead of imparting an impact to the starter ST or the casting M3 by the pulling-up device. Accordingly, the relative displacement produced between the casting M3 and the held molten metal M2 is much smaller, thus allowing prevention of an influence on the shape of the casting M3 as a whole.

Second Embodiment

A free casting apparatus in accordance with a second embodiment will next be described with reference to FIG. 5. FIG. 5 is a cross-sectional view of the free casting apparatus in accordance with the second embodiment. The free casting apparatus shown in FIG. 5 includes an oscillator 107 a as an impact imparting portion when compared to the free casting apparatus shown in FIG. 1. Other configurations of the free casting apparatus shown in FIG. 5 are the same as the free casting apparatus shown in FIG. 1, and descriptions thereof will be omitted.

The oscillator 107 a finely oscillates in a constant period, thereby imparting fine impacts to the starter ST in constant periods. Accordingly, discontinuous shapes are finely formed at constant intervals on the surface of the casting M3. In other words, fine protrusions and recesses are formed on the surface of the casting M3. This enables improvements in design and heat dissipation of the casting M3.

Further, the oscillator 107 a is moveable along a moving path of the starter ST. For example, the oscillator 107 a is moveable in an upward direction following an upward movement of the starter ST by a pulling-up operation of the pulling-up device (not shown). Alternatively, the oscillator 107 a may be fixed to the starter ST while contacting therewith. Accordingly, the oscillator 107 a can impart an impact (oscillation) to the starter ST anytime during the progress of casting.

As described above, the free casting apparatus in accordance with this embodiment includes the oscillator 107 a which imparts fine impacts to the starter ST in constant periods as the impact imparting portion. Accordingly, the free casting apparatus in accordance with this embodiment can form discontinuous shapes at constant intervals on the surface of the casting M3 produced by the continuous casting. Therefore, the free casting apparatus in accordance with this embodiment enables improvements in design and heat dissipation of the casting M3.

Further, the free casting apparatus in accordance with this embodiment imparts impacts to the starter ST in constant periods by use of the oscillator 107 a to allow the held molten metal M2 to oscillate and can thereby enhance the surface tension of the held molten metal M2. Accordingly, the free casting apparatus in accordance with this embodiment can reduce the difference between the shape of a left-right cross section of the held molten metal M2 adjoining the solidification interface (which is the shape of a left-right cross section of the casting M3) and the shape of a left-right cross section of the held molten metal M2 adjoining the shape determining member 102. Therefore, the casting M3 in a desired shape can be shaped more precisely.

Further, the free casting apparatus in accordance with this embodiment imparts impacts to the starter ST in constant periods by use of the oscillator 107 a to allow the held molten metal M2 to oscillate. This enables refinement of crystal structures in the casting M3, facilitation of breakage of a surface oxide film of the held molten metal M2, and an, improvement in bonding strength between the starter ST and the molten metal M1.

It should be noted that the present invention is not limited to the above embodiments but can appropriately be modified. 

1. An up-drawing continuous casting apparatus comprising: a holding furnace which holds molten metal; a guide-out member which guides the molten metal out from a surface of the molten metal held in the holding furnace; a shape determining member which is arranged to adjoin the surface of the molten metal and allows the molten metal guided out by the guide-out member to pass through the shape determining member to define a shape of a cross section of a casting; a cooling portion which cools the molten metal after the molten metal passes through the shape determining member; and an impact imparting portion which imparts an impact to the guide-out member or the casting.
 2. The up-drawing continuous casting apparatus according to claim 1, wherein the impact imparting portion imparts an impact to the guide-out member or the casting by striking the guide-out member or the casting with a metal rod.
 3. The up-drawing continuous casting apparatus according to claim 1, wherein the impact imparting portion moves along a moving path of the guide-out member.
 4. The up-drawing continuous casting apparatus according to claim 1, wherein the impact imparting portion is an oscillator.
 5. The up-drawing continuous casting apparatus according to claim 4, wherein the impact imparting portion is fixed to the guide-out member while contacting with the guide-out member.
 6. An up-drawing continuous casting method using a casting apparatus including: a guide-out member which guides molten metal out; a shape determining member which defines a shape of a cross section of a casting; and an impact imparting portion which imparts an impact to the guide-out member or the casting, the method comprising; guiding the molten metal out by the guide-out member to allow the molten metal to pass through the shape determining member, cooling the molten metal after passing through the shape determining member; and imparting an impact to the guide-out member or the casting by the impact imparting portion.
 7. The up-drawing continuous casting apparatus according to claim 6, wherein imparting an impact to the guide-out member of the casting is carried out by striking the guide-out member or the casting with a metal rod by the impact imparting portion.
 8. The up-drawing continuous casting method according to claim 6 further comprising; moving the impact imparting portion along a moving path of the guide-out member.
 9. The up-drawing continuous casting method according to claim 6, wherein the impact imparting portion is an oscillator.
 10. The up-drawing continuous casting method according to claim 9, wherein the impact imparting portion is fixed to the guide-out member while contacting with the guide-out member. 